A brazen bandit robbed three Brooklyn banks in fewer than 30 minutes today — walking away with cash from two of the heists, police said.

The thief’s first target was the Apple Bank on Kings Highway near Avenue J in Flatlands at 2:15 p.m. He passed a note to the teller and fled with an undisclosed amount of cash, cops said.

Minutes later, he passed a note to a teller at a Capital One Bank also on Kings Highway. That time, he fled empty-handed, authorities said.

But the crook ended his bank-robbing spree on a good note — at an HSBC in Midwood on Kings Highway and East 17th Street at 2:40 p.m., where he fled with an unknown amount of money, police said.

The suspect is believed to be in his 20s or 30s, authorities said.